There are known reel-ups of a paper machine or the like in which the web to be reeled is guided over a reeling cylinder, through a nip formed by the reeling cylinder and the reel being formed, and onto the reel that is being formed. Typically the reel that is being formed is completed around a so-called reel spool which is supported at its ends by means of bearings on so-called reeling rails along which the reel spool and the roll thereon are capable of rolling by means of bearing housings.
Reel-ups of web-like materials are used to reel a material passed in a continuous web into a tight reel, so that it can be moved to further processing. In reel-ups of a paper web, a continuous paper web passed from a paper machine, coating machine or corresponding paper processing apparatus is reeled around a reeling axle, i.e. reel spool, to form a reel. For example, in a so-called Pope-reeler, or in a center-drive assisted Pope-reeler, the finished paper is reeled around the reeling axle after the calender. The web is passed to the reel via a rotatably arranged reeling cylinder, against which the reeling axle is loaded by means of a loading device located in connection with the reeling axle.
The web is passed to the reeling axle so that it is pressed against the preceding layers of the reel and the mantle surface of the reeling cylinder. At this point where the web enters in contact with the preceding layers on the reel, the web is, due to the aforementioned loading device, subjected to a certain nip load, linear load. In present-day reel-up types, the reeling axle is also centre-driven, and by means of the torque of the reeling axle it is also possible to affect the peripheral force of the reel to be reeled. The reeling nip between the reeling cylinder and the reel primarily prevents the access of air to the reel. By controlling the load directed to the web, it is, however, also possible to control the tightness of the reel that is being formed, and in addition, the aim is to change the loading during the reeling process so that the tightness of the reel would comply with the quality requirements set by the paper grade and the after-treatment in different sections in the radius of the reel. The reeling process is controlled indirectly by adjusting the reeling parameters (linear load, web tension, peripheral force and reeling force). The adjustment is typically made with a special program. The main aim of the reeling is to reel a continuous paper web to form a reel which fulfills the requirements set by the reeling process and further processing with respect to processibility and thereby the structure of the reel as well as the paper quality. At present, the speeds of paper machines are typically 20 m/s or higher, and naturally, the aim is to attain speeds which are even higher. The reeling apparatus must operate without interruptions and receive the continuous paper web passed from the preceding sections of the paper machine.
When the old reel has become full, the web has to be cut and the winding of the web following the cut-off point around a new reeling axle has to be started. In practice, this takes place in such a way that when the paper roll formed around the reeling axle has accumulated into its full size, a new empty reel is transferred, typically simultaneously and from above the reeling cylinder, onto the surface of the reeling cylinder, while the paper web is left therebetween. The full paper reel is transferred away from the reeling cylinder, and thereafter the paper web is cut with a suitable way and the end of the web following the cut-off point is guided onto the perimeter of an empty reeling axle, onto which the new web begins to accumulate to form a reel. Thereafter the new reeling axle is transferred to a reeling carriage, travelling on separate linear guides, or on top of horizontal reeling rails. The reel that has become full is transferred e.g. by means of a transfer device along the reeling rails to an unloading station, and at the same time a new reeling axle is brought onto the reeling rails. During the initial reeling process the loading is controlled by means of force devices of the initial reeling device, and when the reeling axle has been transferred e.g. to the reeling carriage, the loading is controlled by means of force devices coupled to the reeling carriage, typically by means of pressurized medium operated cylinders.
For example U.S. Pat. No. 4,634,068 discloses a reeling apparatus in which an empty roll is lowered in contact with the reeling cylinder. Furthermore, a separate mention is to be given to the force devices of the initial reeling device in the U.S. Pat. No. 4,634,068, i.e. a separate loading cylinder and a relief cylinder, and when the reeling axle is on top of the reeling rails, to a loading cylinder which presses the axle against the reeling cylinder. The used hydraulic cylinder is coupled e.g. to swinging arms articulated turnable in the frame of the reel-up.
The properties of the web affect the quality of the reel. For example, the most common reeling problem caused by a bad web tension is the wrinkling of the slack parts of the web, typically the edges, in the reeling nip or nips, because the web is longer by the slack section than by the tight section. The slackness of the edges also causes a poor edge zone in the reel and thereby edge reels of poor quality which are difficult to be reeled by means of slitter winders, and whose problems occur when the rolls are used, for example in printing machines. If the web tension profile varies a great deal or is e.g. uneven, it may lead to the use of high web tension just in case, which stresses the tight sections in the web more and increases the number of web breaks.
In a control circuit of a reel-up which is disclosed in the U.S. Pat. No. 5,285,979, the loading takes place in the frame of the reel-up by means of a carriage moving along linear guides in the frame of the reel-up, to which carriage the loading force device is coupled. In the publication, the reeling axle is arranged in a swinging arm articulated turnable in the carriage, which swinging arm, however, is stationary during the loading and is only used when the reel that has become full is removed by turning the swinging arms to the direction of removal by means of special unloading cylinders. The aforementioned force device is used to supply the desired loading force or to transfer the reeling axle further away from the reeling cylinder as the size of the roll grows. In the initial reeling device this can also take place by means of separate relief cylinders, as is presented in the U.S. Pat. No. 4,634,068. By means of relief cylinders it is possible to compensate the effect of gravity on the reeling cylinder, and thus they are used for so-called profiling. It is also common that in the initial reeling device the loading, relieving and adjustment of the position of the reeling axle with respect to the reeling cylinder are effected by means of one double-acting pressurized medium operated cylinder.
The U.S. Pat. No. 5,285,979 also describes the use of a hydraulic cylinder separately in a situation where the reeling cylinder and the growing reel are kept within a distance from each other, wherein a photocell is used to produce the signal effecting the transfer. The actual loading force is affected by several factors, such as friction caused by the motion of the force device as well as kinetic friction of the structure supporting the reeling axle when it is moved. It should also be noted that the current regulator means is a servo valve which controls the cylinder functioning as a force device, whereas the cylinder controls only one of the two carriages.
There are also known reel-ups such as the one presented in EP patent 604558 and in the related U.S. Pat. No. 5,393,008. The patent discloses carriages arranged movable linearly in guides parallel to the reeling rails, the position of the carriages being determined on the basis of hydraulic cylinders coupled between the frame of the reel-up and the carriages. Thus, by means of these hydraulic cylinders, the location of the reeling axle is at the same time also adjusted with respect to the reeling cylinder. The carriages are provided with separate pressing devices which press the bearing housings located at the ends of the reeling axle and resting on the reeling rails with an adjustable force towards the reeling cylinder to produce the necessary nip pressure. On the other side of the bearing housing, the carriages are also provided with positioning devices by means of which the location of the reeling axle in the carriage can be adjusted more accurately.
In the above-described cases to control e.g. the reeling carriage, the initial reeling device and the loading device, hydraulic cylinders are typically used in pairs to control the different ends of the reeling axle. Thus, the control of the ends is arranged for example by means of an integrated carriage or a carriage arranged in connection with each end to move independently. Furthermore, it is thus possible to arrange the linear load between the machine reel and the reeling cylinder to vary also in the transverse direction of the paper web. On the basis of the above-described facts it is obvious that for the sake of reliable function, the control of the force devices must also be reliable and simple.
There are, however, considerable problems and drawbacks related to the prior art. Thus, such reel-ups entail factors which disturb the reeling process. The rolling surfaces of the reel spools which thus function as surfaces transmitting e.g. supporting force in the support of the reel during the reeling, are subjected to considerable stress when the reel spools are manipulated and driven. These surfaces can also be damaged with time, which impairs the situation even more. Even though the surfaces remained in a relatively good shape, friction is always produced in the rolling which friction is also affected by the mass of the constantly growing reel. This friction also affects the control of the reeling process, such as the adjustment of the linear load.
Thus, in the reeling of a web, particularly as the reel is accumulated, the most significant disturbance factors in the linear load and its control include the changes in the frictions produced as a result of the transfer of the machine reel, i.e. the reel spool.
The essential steps of the reeling process include the change of the reel and the act of stopping the rotary movement of the reel. Thus, as the reel-up in question is a continuous reel-up, the reel has to be removed from the nip contact i.e. from the reeling cylinder constituting the actual reeling nip, at least when stopping the reel. Thus, it is advantageous to form a separate nip by means of a pressing device to bind the surface layers of the reel and to prevent the access of air between the layers of the reel. A pressing device of this kind, such as a roll is, however, impractical with respect to the movement of the operating personnel, because it is typically placed slightly above the machine level. Such a pressing device can be placed and supported by means of an apparatus, such as a slide structure or guides, which is movable separately, wherein it can be driven to the front, i.e. in the vicinity of the reeling cylinder. Such a solution is, however, complicated, and it increases the sequence times.